I converted my old KHS 10-speed into a 1x5, I simply unbolted and removed the small chainring, and removed the front derailleur assembly and cable/shifter.

The chain will not pop off the chain ring unless you do a super bunny hop off a curb, it has never happened to me.

There's a small hill on my commute but I have no problems doing it with the large ring/2nd largest in the back combo, I only use the largest gear in the rear to get started from a red light fast if I need to go across a freeway ramp.